Interpreting respiratory oscillometry in adults with asthma or COPD: findings of an international Delphi study

Background Respiratory oscillometry measures the physiological effort and mechanics of moving air in and out of the lungs during normal breathing. It provides complementary information to spirometry. Uncertainty regarding the interpretation of oscillometry is a barrier to routine use. The aim of this study was to aid in oscillometry interpretation among adults with asthma or COPD by generating expert consensus statements. Methods A Delphi method was used to develop consensus statements regarding the clinical use of oscillometry in adults to identify abnormal lung function, bronchodilator response and minimal clinically important differences. Initial statements were refined in the brainstorming round. Statements were assessed by 60 pulmonologists over three rounds, with consensus defined as ⩾70% agreement. Results Pulmonologists agreed that oscillometry is clinically useful to assess abnormal lung function and its severity, and to measure bronchodilator response. High consensus was reached for resistance at 5 Hz (R₅, 85%), reactance at 5 Hz (X₅, 79%) and area under the reactance curve (A_X, 77%) based on z-scores, where >1.64 was considered abnormal for R₅ and A_X and < −1.64 was considered abnormal for X₅. For measuring bronchodilator response, good agreement was based on using percentage change for R₅, X₅ and A_X. Discussion This international Delphi study combined evidence-based and expert opinion to inform clinicians in the interpretation of respiratory oscillometry. Focusing on a few key parameters of oscillometry will allow clinicians to become confident in its everyday use to assess abnormal lung function, grade severity of impairment, monitor progression over time and assess bronchodilator response.